1. Field of the Invention
This invention relates generally to a drying apparatus and system for treating and curing coatings on wood articles and, more particularly, to apparatus and method that, in one continuous process, applies a protective coating to a wood article, dries the protective coating, paints the coated article and then cures the paint to provide a ready-to-use wood article.
2. Description of the Prior Art
Prior to assembly of windows or door frames, manufacturers have had to treat the unassembled wood frame components with wood preservatives such as fungicides and the like to prevent the wood from rotting. In order to maintain the dimensional stability of the wood frame, waxes and other materials known as stabilizers are impregnated into the wood components to prevent the wood from absorbing moisture.
Typically, the fungicides, stabilizers and the like are applied at the same time by immersing the wood frame components in a solution containing both the fungicides and the stabilizers.
After applying a coating of treating solution to the wood frame component, the coating is allowed to air dry on the surface of the wood. The wood frame component can be left to air dry (i.e., in an unpainted condition) for later painting by the homeowners; however, in some instances it is desired to paint the coated frame component before it is assembled in the frame.
Various radial dipping methods and apparatus are known in the art. Typical apparatus are shown in U.S. Pat. Nos. 3,779,034, 1,274,830, 1,997,013 and 4,299,189. Basically, these patents teach radial dipping methods for quenching molten steel, pickling and electroplating conduit pipes, applying sealant to metal cans, and impregnating plates.
U.S. Pat. No. 2,559,286 teaches a vertical dunking method that applies preservative to wood articles by dropping the articles from a sufficient height so that the articles completely submerge themselves in a dipping tank.
Basically, the aforementioned apparatus and methods are unsuitable for applying treating solutions to wood articles such as window and door frame components. In order to treat window and wood frame parts, the art conventionally uses a bulk treating method which involves pallet treating of stacks of articles by immersing a pallet load of stacked articles directly into a large open top tank containing a treating solution.
The pallet treating is disadvantageous for a number of reasons. First, when a stacked pallet load of articles are dipped into the liquid preservative the stacking prevents direct contact of the preservative to the areas in which the wood articles are stacked on one another. Second, the pallet dipping apparatus generally requires large open dipping tanks (2,000 gallons or more) which have a large surface area for escape of toxic chemicals into the environment. Third, the wood articles have to be immersed in the liquid preservative for sufficient time to allow the solution to seep between the stacked articles which oftentimes permits as much as 30 pounds of excess preservative to seep into the pallet load of wood articles. Fourth, the wet, saturated wood articles are air dried for 48 hours, which permits escape of toxic chemical gasses into the environment. Fifth, the 48 hour in-process inventory stockpile severely delays further processing of the wood articles. Sixth, in order for the pallet system to operate properly and safely, the voluminous escape of the toxic chemical gasses requires costly installation of a large-scale ventilation system.
While the vertical dunking method taught by the U.S. Pat. No. 2,559,286 overcame some of the shortcomings of the pallet dipping method, it is still ill suited for inline coating of wood articles because it is subject to uneven coating produced by turbulence created by plunging the article into the treating solution.
In contrast to the pallet dipping method, the present invention permits one to apply a preservative to the exterior surfaces of a single wood article and have the wood article ready for painting in a matter of a few minutes while prior art process such as the pallet dipping process requires 48 hours or more to air dry the article.